Neither Soviet nor American space scientists knew about the sulfuric acid in Venus's atmosphere in 1966. They thought it was made of mostly nitrogen and were surpised by the results of Venera 4 when it found mostly carbon dioxide.

This is not invalidating that a nickel medallion could survive all the way to the planet's surface, though, especially since it was also encased in a globe of Earth. I am just saying the Venera designers did not plan on dealing with sulfuric acid at the time - though they did design the landers to float in a liquid since it was still believed that the planet was covered in either a sea of seltzer or oil!

My question now is, knowing Venus' seriously harsh environment now, would the medallion and globe still be on the surface in any recognizable form? In Cosmos Carl Sagan emphasized how the Venera 9 and 10 landers, which touched down in 1975 and returned the first surface images of Venus, are slowly corroding in the air.